Robius

A collection of crates for accessing system features (platform APIs) in a cross-platform manner from Rust applications.

These robius crates have a few design goals and major advantages compared to other platform feature abstraction crates:

• They cleanly abstract across both desktop and mobile platforms, so your app code doesn't have to worry about platform-specific code or special cases for different classes of platforms.
• They're quite easy to use from your app (or another Rust library, if desired).
  • In general, they "just work" without any special setup or plugin-like registration. You just add the crate as a dependency and start using it, especially with the Makepad UI toolkit.
  • They should also easily work with other UI toolkits, but may require a small amount of setup. Feel free to file an issue if you find any of them difficult to use with your UI toolkit or Rust app setup.
• Each crate brings in minimal dependencies; we shoot for fast compile times and small object size.
  • If larger dependencies are needed for some features, we keep those optional wherever possible.
• Sane default behavior. We like to keep apps simple, so these crates are mildly opinionated and typically do what you would want by default. But you can customize their behavior as needed, too.

See the below Summary section for more info, or look at each individual crates' docs in crates/. There's also a status table that shows what each crate supports on each platform, and what platform API it uses under the hood.

Summary of included crates

• robius-authentication: asks the OS to show a native authentication prompt to verify the user.
  • TouchID & FaceID on Apple, Windows Hello on Windows, a BiometricPrompt on Android, and a polkit prompt on Linux.
  • Can also fall back to password entry on most platforms, if the OS permits it.
• robius-directories: provides the canonical directory location where each platform wants your app to store its config, cache, data, downloads, etc.
  • This uses XDG defaults on Linux, Known Folders on Windows, Standard Directories on macOS/iOS, and Context.getFilesDir() on Android.
  • Basically just a fork of the now-archived directories crate, with Android support added (using our robius-android-env crate). Note that only ProjectDirs is implemented on Android, which is really the only thing your app probably needs.
• robius-file-picker: shows the OS's native open file, save file, or media picker dialogs/popup.
  • On desktop, this is a thin wrapper around rfd.
  • On iOS, we use UIDocumentPickerViewController and PHPickerViewController.
  • On Android, it uses ACTION_OPEN_DOCUMENT/ACTION_CREATE_DOCUMENT, the system Photo Picker, or MediaStore.Downloads based on the current Android version (that's automatic, you don't have to pick it yourself).
• robius-location: gets the device's geolocation from the OS, and handles the permission prompts for you.
  • Differentiates between an OS's cached location and a fresh (just-retrieved) location.
• : opens a URI/URL in the default system app.

Platform status table for each crate

Symbol legend: ✅ fully supported · ⚠️ partial, or has issues · 🚧 under construction · ❌ not supported

Crate	macOS	iOS	Android	Windows	Linux
robius-authentication	✅ LAContext (LocalAuthentication): TouchID + username/password	✅ LAContext (LocalAuthentication): TouchID / FaceID / PIN	✅ BiometricPrompt + screen lock	✅ UserConsentVerifier (WinRT) for Windows Hello, with username/password fallback	✅ polkit prompt via the desktop's auth agent (needs a .policy file)
robius-directories	✅ Apple Standard Directories (~/Library/...)	✅ Apple Standard Directories (in app sandbox)	✅ Context.getFilesDir(), getCacheDir() etc. via robius-android-env	✅ Known Folders API	✅ XDG Base Directory / User Directory
robius-file-picker	✅ NSOpenPanel, NSSavePanel (via rfd)	✅ UIDocumentPickerViewController, PHPickerViewController	✅ ACTION_OPEN_DOCUMENT, ACTION_CREATE_DOCUMENT, system Photo Picker, MediaStore.Downloads	✅ IFileDialog (via rfd)	✅ XDG portal FileChooser (via rfd)

Version requirements

Each crate has its own Minimum Supported Rust Version (MSRV), typically 1.77, but we try to keep it as low as possible.

On Android, most crates support API Level 26 and up (Android 8.0), but we're always extremely careful to check the API level at runtime and only use features that are available. So you generally don't need to worry about that at all.

Crate	MSRV	Android API Level
robius-authentication	1.77	28 for biometrics, 29 for password fallback
robius-directories	1.64	None
robius-file-picker	1.88	26
robius-location	1.77	26
robius-open	1.72	None
robius-share	1.77	26)
robius-web-auth-session	1.71	Unsupported

Common behavior/conventions in robius crates

Calling from the main UI thread

Due to platform requirements, most functions exposed by robius crates need to be invoked from the main UI thread. This is enforced at runtime and will return an error if mis-used.

The one exception is robius-file-picker, which can be invoked on any thread (it will jump to the main thread if the platform requires it), and the "file picked" callback always gets run on a separate native OS thread.